Current systems and methods for measuring the haze spatial distribution of a semiconductor wafer may involve the use of an atomic force microscope. An atomic force microscope may be used to measure surface roughness of a micro area of the wafer, calculate the power spectral density, and then use the measurements for the micro area to extrapolate the roughness of the entire surface area of the wafer using computer aided calculations.
Another method for measuring the haze distribution of a semiconductor wafer may involve a surface scatter inspection system and measuring the light scattering intensity at specific areas of the wafer.
There also exist methods for determining scattering signal of defects on the surface of a wafer. For example, one existing method involves using the refractive index and absorption coefficient in computer-aided simulation. The optical aperture of the inspection tool may be designed based on a simulation of the defects and a calculation of the signal-to-noise ratio.
The existing methods for measuring haze and defect signal spatial distribution may present a variety of inadequacies. For example, atomic force microscope measurements may be slow and provide detection that is so localized that it is not truly representative of the wafer as a whole. In addition, atomic force microscope measurements may not provide direct light scattering property of a wafer.
The existing methods for measuring haze spatial distribution may also involve determining haze spatial distribution by extrapolating the measurements from a portion of the wafer to the remaining surface area of the wafer. Using a limited area to extrapolate the haze spatial distribution may not provide the level of accuracy needed to meet performance requirements of scatter based inspection systems. In addition, manual methods of measuring haze spatial distribution may not be repeatable.
The many shortcomings of current techniques give rise to a need for a repeatable method and apparatus for measuring haze spatial distribution as well as the defect scattering to haze scattering spatial distribution ratio of a wafer.